A survey team uses an ultrasound transducer at the surface of a flooded quarry. The transducer sends a pulse vertically downwards.
The first echo is produced at the top of a layer of sediment. The second echo is produced at the boundary between the sediment and the solid rock below it.
| echo | time after pulse is sent / ms |
|---|---|
| first | 120 |
| second | 125 |
The speed of ultrasound in the water is 1480 m/s.
The speed of ultrasound in the sediment is 1800 m/s.
Calculate the distance from the transducer to the top of the sediment.
Calculate the thickness of the sediment layer.
The survey team changes to an ultrasound pulse with a higher frequency.
Give one reason why this could improve the measurement of a thin sediment layer.